1. Technical Field
Aspects of the present invention relate to a liquid discharge head for discharging liquid.
2. Description of the Related Art
Voltage is applied to a recording element (a heater) provided on a liquid discharge head to cause the heater to generate heat, causing a discharge port (a nozzle) to discharge liquid. The voltage applied to the recording element (the heater) is supplied by a power source provided on a recording apparatus, to which the liquid discharge head is attached. Such control for discharging liquid from the discharge port has been performed to this date. Japanese Patent Application Laid-Open No. 2002-292875 discusses that a recording element substrate (an element substrate) is provided with a power source regulator for feedback to keep the voltage applied to the heater constant. Japanese Patent Application Laid-Open No. 07-68761 discusses that the timing of a heat signal for driving a heater is shifted within the range of a period 1107 as illustrated in a signal 1101 in FIG. 12 to reduce a noise level occurring in driving a plurality of heaters at the same time.
FIG. 10 illustrates an example in which power is supplied to the recording element (the heater) provided on the liquid discharge head. A flexible flat cable (FFC) 802 and a flexible printed-circuit board (FPC) 805 are provided on a power source line for supplying power from a power source substrate 801 to an element substrate 807. The FFC 802 and the FPC 805 have a parasitic impedance 902. Driving a plurality of heaters causes a problem that the parasitic impedance 902 makes rising and falling waveforms of a current pulse of the heater dull as illustrated in FIG. 11.
In the recording apparatus, a distance between the surface of the element substrate 807 and a recording medium 808 is short. Furthermore, an ink flow path is formed on the back of the element substrate 807. This makes it difficult to arrange a component for reducing the parasitic impedance 902 (for example, a bypass capacitor) near the element substrate 807. For this reason, the parasitic impedance 902 cannot be removed.
Even if the configuration discussed in Japanese Patent Application Laid-Open No. 2002-292875 is adopted, the dullness of rising and falling waveforms caused by the parasitic impedance 902 outside the element substrate 807 cannot be inhibited.
Even if the configuration discussed in Japanese Patent Application Laid-Open No. 07-68761 is adopted, and if attention is focused on current flowing to one heater, periods during which much current such as current 1105 and 1106 illustrated in FIG. 12 flows are caused. Thereby, a current waveform different for each heater is applied to heaters to make the discharge amount of ink different, as a result, degrading the quality of an image to be recorded on the recording medium.